Recently, in a surgery for treating a lesion of a patient, an image-guided surgery using a pre-captured image is widely utilized. In particular, when a surgery is to be performed, high accuracy in performing the surgery without jeopardizing important nerves and major organs in a body of a patient is required based on the images captured in advance.
In general, images captured in advance include three-dimensional images obtained by MRI imaging, CT imaging, or the like. At the start of a surgery, it is necessary to perform registration to match a coordinate system of the three-dimensional images captured in advance with a coordinate system of a patient. While the surgery is in progress, it is necessary to determine in real time a change in position and posture according to a movement of the patient and a surgical instrument. In addition, when the posture of the patient is changed during the surgery, there is a need to perform re-registration to re-match a coordinate system of the patient with the three-dimensional images captured in advance to continuously track the patient or a lesion.
In the related art, a dynamic reference base (DRB) has been used for such registration and tracking. That is, after the DRB is attached to a patient, a three-dimensional image such as CT or the like is captured. Then, at the start of a surgery, registration is performed to match a coordinate system of the three-dimensional image with a coordinate system of the patient. While the surgery is in progress, a surgical instrument is tracked based on the DRB, thereby tracking the position or the like of the surgical instrument relative to a lesion of the patient. In this case, for the purpose of registration, it is necessary to capture a three-dimensional image in advance while keeping the DRB attached to the patient. For accurate tracking, it is necessary to firmly attach the DRB to the patient.
To this end, in the related art, several methods have been adopted such as a method for sensing and tracking a marker after implanting the marker in a bone of a patient, a method for sensing and tracking a template to which a marker is attached by having a patient bite the template with his or her teeth, and a method using a STAMP (Surface Template-Assisted Marker Position) processed by generating an artificial structure.
However, the above conventional methods suffer from a variety of problems such as the difficulty involved in attaching the marker, side effects caused by implanting the marker in the bone, a reduction in accuracy and reliability attributable to the change in the marker position which may be generated when the marker is bitten by teeth, inconvenience in manufacturing an expensive STAMP before a surgery and the substantial time and cost required for manufacturing the STAMP, etc. Moreover, in the case of the conventional methods, even when the DRB is firmly attached to a patient, if the patient moves, the distance between the DRB and the lesion of the patient or the posture of the patient may change. Thus, accurate tracking cannot be carried out and re-registration cannot accurately be performed, thereby resulting in a problem that the DRB cannot be used. Accordingly, in the case of the conventional methods, a surgery is performed under the assumption that the patient does not move. In practice, however, it is often the case that a patient moves during a surgery. Thus, it is difficult to carry out the tracking in a substantially accurate manner.
Accordingly, there is a need to develop a registration method capable of acquiring an accurate registration result in a shorter time and with a reduced cost. Further, there is a need to develop a tracking system and tracking method in which tracking is performed in a relatively accurate and easy manner even if a patient moves or the posture of the patent changes during a surgery.